In one of the posts I've read that currently service tasks are not suported in import/export and that I will need to wrtie my own custom class which extends ShellTaskBehaviour class. I am also unable to locate the ShellTaskBehaviour class. Please specify the jar in which this class is present and how can I use it to write my custom shell task. here the link to that post :

I would like to know how to execute my shell scripts using bpmn file. And if the import/export of service tasks is not currently supported then will it be implemented in the future releases and whats the best way to implement the shell tasks :)

In order to run shell commands or any potentially "long" activity, I usually model an human task assigned to a "system" group or user. You can then use a task listener that starts the desired command asynchronously. When the command finishes, it uses Activiti's api or rest to complete the task.